The dredging of the bottoms of bodies of water usually takes one of two forms, suction dredging or shovel dredging. Each system has its own advantages and limitations as discussed below.
In underwater suction dredging operations the apparatus consists of a vessel or barge floating upon the water surface and the inlet of a pump suction system is positioned below the barge permitting the pumping, and removal, of a slurry formed by the bottom materials and water. Cutterhead apparatus is normally associated with the suction conduit inlet having cutter and agitating elements, often power-driven, for loosening the bottom material and conveying the loosened material toward the suction conduit and large volumes of material can be continuously handled.
While a wide variety of suction dredge cutterheads have been proposed and used with suction dredges, cutterheads using continuously rotating augers, knives, tools and the like are most advantageously utilized where the bottom material is relatively soft and free of large rocks, stumps and similar hard foreign objects. Also, cutterheads of the rotating cutter type, or which use hydraulic jets to loosen the bottom material, are relatively ineffective in handling heavy consolidated bottom soil and material, and such cutterheads are easily damaged in such environments.
In shovel dredging systems buckets are used and the bucket is manipulated away from or toward the operator to "scoop" the bottom material into the bucket and the bucket supporting apparatus is operated to raise the loaded bucket above the water level and deposit the dredged material ashore, or in an adjacent barge or other container capable of receiving the material from the bucket.
While the use of shovel bucket dredges permits the dredging of water bottoms having heavy consolidated material, large rocks, stumps and the like, such operations are slow, expensive and inefficient, in that the bucket must be raised, swung and moved substantial distances and unloaded, and movement of the bucket upwardly through the water will wash much of the material from the bucket prior to unloading.
Where the dredge is being used to mine the water bottom material, such as in gold mining operations, the tendency for the dredge material to "wash" from the shovel bucket as it is moved upwardly through the water is particularly troublesome in that valuable material may be lost, and only a portion of the material originally contained in the bucket is retained for processing.
It is an object of the invention to provide a shovel dredging system utilizing a suction pump for handling the dredged material wherein the advantages of suction and shovel dredging systems are combined and the disadvantages are eliminated.
Another object of the invention is to provide a shovel dredging system wherein the bottom material is accumulated within the shovel bucket and is continuously removed from the shovel bucket by the suction conduit of a suction pump system.
Yet another object of the invention is to provide a shovel dredge system using a dredging bucket and a pump suction line to directly remove the dredged material from the bucket to minimize the manipulation of the shovel during operation.
An additional object of the invention is to provide a shovel dredging system wherein the dredged material is directly removed from the shovel bucket by the suction conduit of a pump system and guards and screens are used with the shovel and suction conduit to prevent the entrance of oversize particles into the conduit.
A further object of the invention is to provide a shovel dredge system wherein a pivotal shovel bucket is in communication with the suction conduit of a pump system, and the configuration of the suction conduit and bucket include segments concentric with the bucket pivot axis to prevent interference during bucket movement.
In the practice of the invention a power-operated shovel apparatus is mounted upon a floating barge. The barge may include vertically extendable jacks and stabilizers for engaging the bottom material of the body of water being dredged to improve stability. In the disclosed embodiment processing apparatus is mounted upon the barge for sorting and separating the dredged material for gold mining purposes, and while the inventive concepts are advantageously utilized in the mining of submerged material, the apparatus may, likewise, be advantageously employed for conventional dredging operations wherein the purpose is to remove bottom material and spoils from the waterway to increase the depth, form channels, etc. In the disclosed embodiment the shovel apparatus is of the hydraulic type consisting of a plurality of pivotally interconnected linkages or arms whose relative relationships may be adjusted by hydraulic expansible chamber motors. The disclosed shovel apparatus is similar to that commonly known as a "backhoe" and the shovel apparatus is pivotally mounted upon the barge and controlled by valves conveniently located for manipulation by the operator. The free end of the shovel system includes a bucket which is mounted upon the arms and is capable of limited pivotal movement by a hydraulic motor.
A powerful motor-driven pump is mounted upon the barge having an outlet conduit communicating with the processing apparatus, and the pump includes a suction conduit having an inlet end mounted upon the shovel apparatus above the shovel bucket. An evacuation conduit is attached to the shovel apparatus adjacent the bucket and includes an upper end connected to the pump suction conduit, and the lower end constitutes an inlet which is located within the shovel bucket.
Accordingly, as the evacuation conduit inlet is located within the bucket the pump will be supplied with water and dredged material directly from the bucket and keep the bucket relatively "empty" of dredged bottom material.
A grid or screen is usually located over the open end of the bucket to prevent oversize particles from entering the bucket and during dredging the bucket is moved through short forward strokes sufficient to fill the bucket with material, but preventing the bucket from being raised from the water so that air will not enter the bucket and pump system. The evacuation conduit will be continuously removing the water and dredged material from the bucket and a high efficiency of bucket operation is achieved in that time consuming movements of the bucket are eliminated.
The shovel bucket includes a bottom wall which is of a concave cylindrical configuration having a center coincident with the bucket pivot axis, and the evacuation conduit is provided with a bell shield having a peripheral edge located in a predetermined spaced relationship to the bucket bottom wall. This spacing prevents oversize particles from entering the evacuation conduit, and the concentric relationship of the bucket bottom wall to the bucket pivot will maintain this spacing during bucket pivotal movement.
The bucket also includes a rear wall having an opening defined therein, and the evacuation conduit enters the bucket through this opening. The evacuation conduit includes an elbow arcuate portion located within the bucket opening which is of a configuration concentric to the bucket pivot axis, and this relationship prevents interference between the evacuation conduit elbow and bucket during bucket pivotal movement.
The continuous removal of dredged material and water from the bucket through the evacuation conduit will provide a consistent supply of slurried material to the processing apparatus mounted on the barge. While the manipulation of the shovel apparatus will load the bucket somewhat intermittently the pump suction system will continually remove the dredged material from the bucket and the operator may engage in a substantially "continuous" dredging and digging operation by the shovel apparatus. As the dredged material is removed from the shovel bucket adjacent the bottom wall, heavy material, such as gold, will be drawn into the pump system for processing, and very little material entering the bucket is "lost" due to bucket movement through the water.
The shovel is capable of readily dredging hard consolidated materials and large rocks and stumps will not damage the apparatus. If desired, underwater television apparatus may be attached to the shovel apparatus to permit observation in the area being dredged, and the practice of the invention substantially improves the efficiency of a dredging operation utilizing a shovel.